Jeff Jonas

2016: the year of the
cheap embedded Linux system
and IoT

This is more of a roundup than a product review.

Digikey now stocks Adafruit, Sparkfun and other "hobbyist" items.
There are more kickstarters than ever before.
Innovation is everywhere!

The Raspberry Pi is the clear winner with several formats and price points
There are plenty of Raspberry Pi clones but they are nowhere as well supported:

other embedded Linux systems that are very popular and successful:

The $9 Next Thing CHIP module and $69 Pocket Chip
are very popular in the retro-gaming arena
The BeagleBone Black and BeagleBone Green are embraced by the BSD community.
The Intel Edison Compute Module is heavily promoted at IoT Hack-a-thons.
It is usually paired with a breakout board for Arduino shields.
Citing wikipedia:
The Intel Galileo is not dead yet but is nowhere as well promoted. Galileo G2 datasheet

IoT modules

The $3.00 gumstick-sized ESP8266 WiFi Module and the newer ESP32 Wi-Fi & dual-mode Bluetooth module
were intended to be just a TOE (TCP offload engine) but the ARM core is programmable enough to work stand-alone.
The main variation in breakout boards is the number of I/O pins.
Learn more at
UPDATE: here's an open source competitor to the ESP: lininoOS:
A MIPS GNU/Linux box for Arduino and Internet of Everything.
Combining the Linux OS with IoE HW + certified WiFi 802.11n connectivity and use OpenWRT and Peer-to-Peer (AllJoyn software framework) to customize your own project. The product hopes to make an open source WiFi home automation seamless and easy to understand for all levels of technology users.

other educational microcontrollers

Hack Manhattan (137 W 14th St) holds affordable workshops

new parallel architectures

The Parallella Board

network flow processors by
Parallax 8 core Propeller is open source,
popular for robotics and the Open-source Hackable Electronic Badge

And a time of silly names for expansion boards

DISCLAIMER: these are systems that I have, have encountered or are related to them.
There are hundreds, perhaps thousands of production embedded systems by companies big and small.
Journals such as Circuit Cellar cover them as articles or advertisers.